1. Field of Invention
The present invention relates to a peripheral input device, and more particularly to a specific wavelength selecting method for an optical input device and an optical input device thereof.
2. Related Art
In recent years, with the rapid development and progress of technologies, computer equipment such as a personal computer (PC) or a notebook has become an indispensable convenient tool in people's daily life or work. However, the computer equipment must be installed with a pointer input device such as a mouse, a touchpad, or a trackball to perform manipulations on a window interface of the computer equipment.
Taking an optical mouse as an example, currently, a common optical mouse in a hemispherical domelike structure is only limited to being used in a conventional manner. Actually, due to a large shape and volume of the optical mouse, a user still cannot operate the optical mouse like holding a pen, thereby resulting in a dead angle to a certain extent in use. The conventional optical mouse in a hemispherical domelike structure also causes a lot of inconveniences in use due to the structure and shape designs. In order to solve the above problems, manufacturers have already started to provide an optical mouse with a pen-like structure in the market, which is convenient for the user to hold the mouse in operation, and conforms to the ergonomic habit of holding a penholder.
As disclosed in U.S. Pat. No. 6,151,015, in a pen-like optical mouse as a computer-aided input device, a light-emitting diode (LED) or a laser diode and an optical sensor are disposed inside a pen-like shell. The LED emits and projects light rays on a working surface. The optical sensor is then used to sense changes of light rays refracted back from the working surface and perform imaging, so as to generate a corresponding cursor movement signal and transmit the cursor movement signal to the computer equipment. When the pen-like optical mouse moves, its moving track is recorded as a group of consecutive pictures photographed at a high speed. Finally, an interface microprocessor inside the optical mouse is used to perform analysis and processing on the photographed pictures. Thus, a moving direction and a moving distance of the mouse are determined by analyzing changes of positions of feature points in the pictures, so as to position the cursor.
However, regardless of a hemispherical optical mouse or a pen-like optical mouse, due to the volume restriction, only a single optical sensor and a single LED can be disposed inside the mouse, and the LED can only emit light rays at a single wavelength, thereby causing various limitations on the use of the optical mouse. That is to say, the conventional optical mouse must be very close to a working surface, or even attached to the working surface, such that the requirement on the flatness of the working surface used together with the optical mouse is rather high, so as to ensure the cursor to be positioned successfully.
If the user makes the optical mouse generate up and down movements in the operation process to result in an excessively large distance away from the working surface, or the flatness of the working surface is rather poor, the optical signals represented by the reflected light rays generated after the LED emits the light rays onto the working surface are changed, such that confusion occurs when the optical sensor reads the optical signals, thereby causing a low contrast of the images sensed by the optical sensor, or even causing a situation that the cursor fails to be accurately positioned.